Officials are studying how a lab worker died from a Neisseria meningitidis infection that he apparently contracted while researching the bacterium at the San Francisco Veterans Affairs Medical Center (pictured).

The 25-year-old lab worker was part of a team of researchers who are trying to develop a vaccine against the bacterium, which causes septicemia and meningitis, the Bay Area News Group/San Jose Mercury News reports. The paper reports that the worker felt his first symptoms two hours after leaving work last Friday, grew worse on Friday night, asked friends to take him to the hospital on Saturday and died later that morning.

KQED News identified the man as Richard Din of San Francisco.

Investigators from the California Occupational Health and Safety Department are “investigating the lab worker’s death and whether the lab where he worked followed safety protocols,” and health officials are treating the worker’s friends and family, as well as hospital workers who treated him, with preventative antibiotics.

KQED reports that workers in the lab that employed Din were not vaccinated against several strains of Neisseria meningitidis, including the strain that apparently killed Din.

“This appears to be a violation of [Centers for Disease Control] guidelines, which specify that lab workers handling any type of Neisseria should be vaccinated, even though the vaccine is ineffective against serotype B,” KQED reports.